Photothermographic film generally includes a base material, such as a thin polymer or paper, typically coated on one side with an emulsion of heat sensitive materials, such as dry silver. Once the film has been subjected to photo-stimulation, such as by light from a laser of a laser imaging system, for example, the resulting latent image is developed through application of heat to the film to form a visible image.
Several types of processing machines have been developed for developing photothermographic film. One type employs a rotating heated drum having multiple pressure rollers positioned around the drum's circumference to hold the film in contact with the drum during development. Another type of processor, commonly referred to as a flat-bed processor, includes multiple rollers spaced to form a generally horizontal transport path that moves the photothermographic film through an oven. Regardless of their type, processors are typically designed to heat the photothermographic film to at least a desired processing temperature for a set time, commonly referred to as the dwell time, for optimal film development.
As the photothermographic film is heated, some types of emulsions produce gasses containing contaminants, such as fatty acids (FAZ), which may subsequently condense when coming in contact with cooler air or surfaces within the processor. When contacting cooler air or cooler surfaces, the gasses may condense and contaminants, fatty acids in particular, may become deposited on the photothermographic film and subsequently be transported to other processor components. These deposits can accumulate over time and can damage processor components, cause film jams within the processor, and cause visual defects in the developed image.
In efforts to reduce the occurrence of such problems, processors generally include systems designed to remove the gasses from the processor before the contaminants can condense. These systems generally include a duct or vent system designed to direct a stream of heated air and gasses from a processing chamber through some type of condensate accumulator and then through a filtering module before exhausting the air to the environment.
Condensate accumulators are generally designed to cool the air stream and cause contaminants to precipitate and collect on accumulator surfaces. Condensate accumulators take a variety of forms, ranging from condensation traps that simply mix ambient air with the heated air stream to various forms of heat exchangers. The cooled air stream is passed from the condensate accumulator through the filtering module. The filtering module typically includes an absorbent block which removes odorous materials before exhausting the air stream from the processor.
While the absorbent block of the filtering module is typically replaceable, the condensate accumulator generally remains affixed to the processor. Also, the condensate accumulator and filter module are typically positioned remotely from the processing chamber and require an extended duct system through which to receive gasses from the processing chamber. Due to its distance from the processing chamber, contaminants often condense and accumulate within the duct system. As a result, even though the filter module may be user replaceable, regular maintenance is generally required to remove contaminant build-up from within both the duct system and the condensate accumulator. Such maintenance can be costly and result in processor downtime.
It is evident that there is a need for improving thermal processors to reduce problems associated with contaminants produced during development of photothermographic film.